But the National Rifle Association and other gun-rights advocates paint a dark picture of expanding background checks for private purchases, insisting that the move would inevitably lead to a national firearms registry.

The background check proposal, part of a post-Newtown Senate package facing an uphill climb on Capitol Hill, is "aimed at one thing .registering your guns," said NRA CEO Wayne LaPierre in February. "When another tragic 'opportunity' presents itself, that registry will be used to confiscate your guns."

But apart from the political crossfire, some gun policy experts say they are genuinely baffled over the logic behind the pro-gun side's checks-registry-confiscation equation.

"Except as matter of fantasy, it's inconceivable; it would be laughable if it weren't so frightening," said Dr. Garen Wintemute, director of the Violence Prevention Research Program at the University of California-Davis. "This is pandering to the fears of people in the gun movement. I'm sorry, but it's crazy talk."

Under the Brady law of 1993, only gun sales by federally licensed firearms dealers (who typically own stores) are subject to a check with the National Instant Criminal Background Check System operated by the FBI, which says that over 100 million such requests have been submitted in past decade of which more than 700,000 have been denied.

Schumer's legislation would widen background checks to include gun sales between individuals, including those at gun shows. Private parties would be required to have a licensed firearms dealer complete the sale with a background check.

Exceptions would be made for gifts between family members, temporary loans and, under certain circumstances, gun exchanges among hunters and at shooting ranges and competitions.

Current law requires the FBI within 24 hours to destroy background-check requests that result in approvals, although dealers keep a record of the check.

Schumer aides insist none of this would change under his proposal. The government would not possess background-check data with which to build a registry.

But a one-time Schumer ally on the Republican side, Sen. Tom Coburn, R-Okla., parted ways with the New York Democrat over firearms dealer background-check record-keeping, which Schumer supports and Coburn opposes.

David Kopel, an NRA member and research director at the Independence Institute in Denver who has testified before Congress on guns, said universal background checks would represent a "decentralized" database tantamount to a national registry.

The process could take decades to unfold, he said. "It's more like smoking and cancer smoking does hugely raise the risk of dying of cancer."

Kopel pointed to the United Kingdom, Canada and Australia, which he said all used gun registration and licensing as the basis for seizing weapons that were restricted in the wake of massacres comparable to the one at Sandy Hook Elementary School in Newtown, Conn.

Fear of gun registration and confiscation "has been an NRA mantra forever" said William Vizzard, a criminal justice professor at California State University in Sacramento and formerly an ATF supervisor in San Francisco. "It's based on nothing but the fact they just keep saying it over and over again."

Gerald Nunziato, a former ATF agent who directed the bureau's National Tracing Center from 1991 to 1998, said that under the 1934 National Firearms Act, the ATF is required to maintain a registry of machine guns, sawed-off shotguns, silencers and other weaponry favored by Prohibition-era gangsters.

"If what the NRA says is true, why haven't these weapons been seized?" Nunziato said.

The NRA points to two "smoking guns." One is a Jan. 4, 2013, Justice Department memo, which says universal background check "effectiveness depends on the ability to reduce straw purchasing, requiring gun registration and an easy gun transfer process."

Elsewhere it says gun buybacks are ineffective "unless massive and coupled with a ban." The NRA used the memo in an ad campaign, with NRA lobbyist Chris Cox intoning: "Still think President Obama's proposals sound reasonable?"

But the author, National Institute of Justice Deputy Director Greg Ridgeway, also says the memo is intended to be "a cursory summary" of initiatives to counter gun violence. White House Press Secretary Jay Carney said none of the administration's gun-control proposals "would take away a gun from a single law-abiding American."

The other is a television interview with Schumer in which he states that one of the proposals he's "pushing" is "universal registration." Schumer's aides insist he meant to say universal background checks, a point he made clear elsewhere in the interview.

Schumer has been adamant that a national firearms registry is "already illegal" and his proposal would not create one.

"I would hope and pray we would debate the rational parts of this bill and not say this bill is going to lead to confiscation or registration," Schumer said at a Senate Judiciary Committee hearing March 13.